Synthesis and Characterization of UV-LED Curable Nanocomposite Coatings

Objective: In the present work, the possibility of using UV-LED curing processes for the design of smart nanocoatings showing enhanced thermal, thermo-mechanical and barrier properties was thoroughly investigated. Method: A commercially available ethoxylated bisphenol A diacrylate resin, chosen as a model system, was added to 5 wt.% of an organophilic nanoclay (Cloisite 30B) and a photoinitiator (2,4,6-Trimethylbenzoyldiphenyl-phosphineoxide), suitable for the UV-LED curing process. The system was then exposed to UV-LED radiation and the obtained coatings were characterized. Results: As assessed by infrared spectroscopy and differential scanning calorimetry, a quick exposure (i.e. 5 s) to the UV-LED radiation in dynamic conditions was enough to achieve the completeness of the photocuring reaction. The morphology of the obtained coatings was characterized using X-ray diffraction and scanning electron microscopy: in particular, a clear increase in the interlayer distance was observed, hence indicating the occurrence of intercalation phenomena of the nanofiller into the curable resin. Furthermore, the good interactions taking place between the clay nanoplatelets and the polymer network were responsible for: i) an increase of the glass transition values of the polymer network, ii) enhanced thermal and thermo-oxidative stability of the nanocoatings and iii) improved barrier properties towards oxygen diffusion. Conclusion: The UV-LED curing process was found very suitable for obtaining nanostructured coatings showing decreased oxygen permeability, as well as improved thermal and thermo-mechanical features.